The invention relates to a method, in particular for the manufacture of an expansible anchor consisting of corrosion-resistant steel having an expansible sleeve and an expander body.
Expansible anchors consisting of corrosion-resistant steel having an expansible sleeve slotted for a part of its length and an expander body with an expander cone which is arranged to be driven into the expansible sleeve in order to anchor the expansible anchor are well enough known. When anchoring the known expansible anchor, the high expansion pressure during the anchoring process can lead to binding of the two surfaces of the expander body and expansible sleeve that are in sliding contact with one another. This binding considerably impairs the function of the expansible anchor. Such an anchor is in particular unsuitable for use in the zone subject to tensile forces, since enlargement of the drilled hole as a result of cracks forming cannot be compensated for because of the lack of subsequent expansion behavior.
For that reason, in the case of expansible metal anchors it is customary to use steels of different structural constitution for the two metal parts that are in sliding contact. Since, however, these parts can be manufactured and supplied only in large numbers, this option is not always applicable, especially in the case of stainless steel anchors. Moreover, neither is it possible to achieve an acceptable homogeneity in the structural constitution of the steels which effects a reduction in the tendency to bind with satisfactory reliability.
To reduce the tendency to bind, it is moreover known to provide one or both metal parts with a coating. This coating, which is applied, for example, by an immersion process or by spraying, is very thin and has little resistance. During the anchoring process the coating can consequently be scraped off, so that the sliding behavior for subsequent expansion in the event of enlargement of the drilled hole as a result of cracks forming is considerable impaired. Moreover, such a coating also does not guarantee the long-term behavior of the expansible fixing plug in respect of subsequent expansion.